Aqueous streams are ubiquitous in everyday life. Aqueous streams are invariably an essential element in most residential, commercial, and industrial environments.
In residential and commercial environments, aqueous streams are utilized in indoor and outdoor applications. Indoor applications may include, but are not limited to, lavatories, showers, tubs, toilets, laundry, ice-making, drink dispensing, dish washing, pot fillers, laboratory, cooling and refrigeration, and heating. Outdoor applications may include, but are not limited to, landscaping, water features, spas, pools, washing, or even water attractions in the case of entertainment parks.
Although many of the indoor and outdoor applications of residential and commercial environments can be found in industrial environments, aqueous streams in industrial environments are primarily utilized in the industrial processes required to manufacture a product that may or may not be an aqueous product. For example, in a bottling plant, the final product is a beverage which is an aqueous product. On the other hand, in a fabric plant, although it may use aqueous dying and washing processes, the ultimate product is a solid fabric.
For residential, commercial, and many industrial environments, the source aqueous stream is primarily water. This water source is typically supplied by the local water utility. The local water utility installs a water meter at the water service entrance to a building site.
A fixture for the use of water at a building site is referred to herein as a water fixture. Each water fixture in a water supply system represents a certain maximum demand of water. For example, a clothes washer may have a maximum demand of 6 gallons per minute (gpm) while a bidet may only have a maximum demand of 2 gpm. The maximum demand of each water fixture does not necessarily represent the typical demand from the fixture. For example, a kitchen faucet may have a maximum demand of 3 gpm but may typically be only partially opened to demand only 1 gpm.
The water meter installed by the local water utility is normally sized based on the maximum flow rate from simultaneous demand of all the water fixtures at the site. This total theoretical demand for a water supply system is calculated by adding the maximum demand of all water fixtures at the site. Thus, for example, the local water utility may install a 1″ meter at a site with a theoretical maximum flow rate demand of 50 gpm and a 4″ meter at a site with a theoretical maximum flow rate demand of 500 gpm.
Since typically not all water fixtures are operating at the same time, the typical maximum flow demand can be substantially less than the theoretical maximum flow demand. The quantity and type of water fixtures, in addition to water fixture user behaviors, can greatly impact the variability between the theoretical maximum flow demand and typical maximum flow demand.
The range of water service pressure, in pounds per square inch (psi), at the water meter may vary greatly within a water utility service area. For example for the Southeast San Diego Community Planning Area, encompassing site elevations ranging from 20 feet to 175 feet above mean sea level, the maximum static water system pressure within the planning area ranges from a low of 90 psi to a high of 160 psi.
Pressures lower than 55 psi may result in water fixtures operating poorly. High water pressure into a building site may damage internal plumbing pipes as well as cause water fixtures to malfunction; for this reason, the Plumbing Code requirement requires pressure regulators be installed on all water services greater than 80 psi. High system water pressure is also of a concern to the utility water operations as pipeline leaks or pipeline breaks will be more severe if the system is operating at higher pressures.
Since pressure regulators are part of a building site's private water system, the site owner will typically contract a licensed plumber to install the required pressure regulating valve and make the proper adjustments for the site's water pressure requirements which for residential and commercial applications is typically set between 60 and 70 psi. Over time, pressure regulators can fail due to corrosion or deposit buildup and thus requires that the pressure regulator be checked periodically by a licensed plumber.
Understanding hydraulics, or the study of fluid behavior at rest (hydrostatic) and in motion (hydrodynamic), is essential for installing an effective water distribution system at a building site that minimizes the potential for damage to pipes and water fixtures. Since the water meter typically is located at the water service entrance to a building site it is the first device calculated into a water-distribution system design that inevitably results in having the proper flow and pressure at the farthest water fixture in the building. For a water fixture to operate properly and avoid damage it may not only have the fixture's water flow demand available, but the static pressure at the fixture less the total hydrodynamic pressure loss at the fixture may be greater than the fixture's minimum operating pressure requirement but less than the fixture's maximum operating pressure rating.
Static (hydrostatic) pressure measures water at rest or water that is experiencing no friction or pressure loss due to movement. The formula for water pressure in pounds per square inch (psi) is force (in lbs) divided by area (in inches squared). When the area is constant, the force of water depends on its elevation. One foot of water elevation is equal to 0.433 psi or alternatively stated one psi equals 2.31 feet of water elevation. Fixtures installed at a building site may have significant or minor differences in elevation. For example, a bathroom lavatory faucet installed on the first floor will have a significantly different elevation than a bathroom lavatory faucet installed on the second floor; for illustrative purposes say a 14 foot difference. Likewise a bathroom lavatory faucet installed on the second floor will have a minor difference in elevation compared to a tub faucet installed slightly lower but still on the same second floor; for illustrative purposes say a 6 inch (one half foot) difference. Thus with water at rest, fixtures at a building site will likely have varying static pressures and be different than the static water pressure at the water meter because of the differences in elevation. For the first example above if the first floor bathroom lavatory faucet had a static pressure of 60 psi, the bathroom lavatory faucet on the second floor would have a static pressure of 53.938 psi. For the second example above if the bathroom lavatory faucet on the second floor had a static pressure of 53.938 psi, the static pressure on the second floor tub faucet would be 54.1545 psi.
Dynamic (hydrodynamic or working) pressure measures water in motion or water that is experiencing pressure loss due to friction as it flows through the length of pipes, fittings, valves and other components all of which offer resistance. This dynamic pressure varies throughout the system. The amount of water flowing through the system and the physical size of the path affect friction loss. Friction loss increases as the flow or speed of water (water velocity) through the system increases. If only one water fixture were allowed to operate at any one time and assuming no variability in the flow demand at the water fixture, then the total pressure losses at a water fixture would be a fixed (non-varying) quantity and readily quantifiable. However, since water fixtures at a building site can operate singly or concurrently and further since water fixtures can have varying flow demands (as in slightly open to fully open lavatory faucets) the pressure at different points in the water distribution system at a building site will depend on the number of operating water fixtures at a given moment and the operating demand flow of each fixture at that moment making the pressure loss throughout the system and at each water fixture highly variable.
In addition water pressure at the meter normally fluctuates +/−10 psi, further increasing the variability in hydrostatic pressure delivered to the site. Additionally when repairs or maintenance is being done on the water infrastructure and water is shut off in certain areas to make repairs, the water pressure at the meter will increase above the normal fluctuating range and further impact the variability in hydrostatic pressure delivered to the site.
High water pressure into a building site may damage internal plumbing pipes of the water distribution system as well as cause water fixtures to malfunction causing water to leak at the building site.
In addition to high water pressure, water fixture user error (e.g., user left a faucet open), faulty water fixtures (e.g., defective ice maker), installation error (e.g., inadequate plumbing work), accidental damage to internal pipes or fixtures (e.g., drilling a screw into a water pipe), or aging system components (e.g., corroded pipe) are among other common causes of water leakages at building sites.
A water leak at a building site can range from slow drips to fast gushes. For illustrative examples a dripping leak may spill 15 gallons per day (about 0.01 gallons per minute) while a ½″ pipe break may spill up to 60,900 gallons per day (about 423 gallons per minute).
A water leak may be immediately visible at the water site as in the case of a pipe break or may not be detected until significant time has elapsed as in the case of a small drip behind a wall partition.
Water leaks on the inside of a building site can cause extensive damage to the building structure and to furnishings at the premises requiring significant reconstruction and replacement expense. In addition, interior water leaks may lead to the growth of toxic mold and fungi requiring costly site remediation. Outdoor water leaks can cause damage to the building site's foundation, the building structure itself, as well as damage the landscape plant life. In addition to the damage caused by water leaks, water leaks represent a significant waste of water resources; water agencies estimate that for residential sites, up to 3% of all water consumed is attributable to water leaks.
Because of the expense and liability associated with water leaks, insurance companies have been increasingly placing limits on coverage for damage from water leaks and from toxic mold and fungi. In addition, when water damage has occurred, the property owner has a legal requirement, in the event of an intended property sale, to disclose the occurrence which may negatively affect the perceived value of the property to potential buyers.
Since water leaks are a common occurrence and the consequences represent significant cost, potential liability, and lost value there is significant interest in devising ways to detect and stop water leaks so as to minimize any water damage they may cause.
For industrial environments, because of the sensitivity to flows and pressures within their industrial processes, the monitoring and control of aqueous flows is achieved by installing precision pressure and flow sensors abundantly throughout the process and closely monitoring the sensors using industrial monitoring systems that automatically take corrective action in the event a leak is detected. These sensors are often part of a larger monitoring and control system that encompasses additional measurements (e.g., temperature, chemicals, and viscosity) specific to the industrial process. While it is technically possible, the cost of such an extensive and precise monitoring and control leak detection system is prohibitive for any wide scale adoption at residential and commercial environments. In addition, in residential and most commercial environments the internal pipes and connections to water fixtures are typically not readily accessible for installation of pressure or flow sensors and of control valves across branches of the water distribution system as is the case in industrial environments. Other than while under building construction, in residential and commercial environments the internal pipes of the water distribution system and connections to water fixtures are often located behind walls, underneath or within floors, buried beneath the ground, in attics or crawl spaces, or at other readily inaccessible areas (e.g., behind a large built-in water fixture).
One method that is used for leak detection in residential and commercial environments is water detection beneath the water fixture. In this method, a water detection device, such as an electrical device consisting of two electrodes, is placed beneath water fixtures. The water detection device is most often passive and detects the presence of water when water completes an interrupt circuit between the two electrodes; essentially the water acts like a toggle switch to close a normally open single pole single throw switch. This water detection device is connected, either by wire or wirelessly, to a normally open shut-off valve that controls the flow of the water to the water fixture. When the interrupt circuit is completed (switch is closed) by the presence of water at the water detection device, the normally open shut-off valve is activated to close and thereby stopping any further water flow to the water fixture. This method has many shortfalls. Among the shortcomings is the requirement that a water detection device together with a paired shut-off valve be installed at each and every water fixture. This method assumes that if a water fixture were to leak, the water would flow to where the user has placed the water detection device. If water from a leak were to flow elsewhere, the presence of water would not be detected. In addition, to install the shut-off valve requires basic plumbing knowledge, fittings, and tools, as otherwise an improperly installed shut-off valve will create more opportunity for leaks than if the water detecting device were not installed. Another shortcoming of this method is that there must be electrical power available to enable activation of the shut-off valve. In the case of an AC power requirement, it is uncertain whether an AC outlet will be located near where the shut-off valve for the fixture would need to be installed (e.g., beneath a tub). In the case of battery power, this introduces the requirement of replacing batteries periodically to make sure there is sufficient power to shut the valve if and when a leak is detected. These power requirements would also apply in the case of powering wireless connectivity between the water detection device and the shut-off valve. Another shortcoming of this method is the inability to access the plumbing pipe line to a water fixture. For example, installing this method to a built-in dishwasher would require removing the dishwasher and installing the shut-off valve in such a way that it would not obstruct the dishwasher's placement. This method is also inappropriate for many types of water fixtures; for example, for a shower the placement of the water detection device is not reasonable and placement of the shut-off valve would require major effort and expense to get access to the water fixture's water line typically located behind a water-tight wall. Even in the case where all water fixtures were readily accessible without causing any obstruction by the installation of the device, and where there was a nearby power source at each water fixture to meet any power requirements, and where the water detecting device placement would properly detect any water leaking from the fixture, a typical residential or commercial environment would require numerous devices being installed which would represent a significant expense in the cost of purchasing the devices as well as the cost of properly installing the devices. Perhaps one of the largest shortcomings of this method is that while it may shut-off water to an individual leaky water fixture, many water leaks do not originate at the fixtures themselves but originate from the connections to the water fixtures and from the internal pipes of the water distribution system. These connections and internal pipes, as mentioned above, are not readily accessible and further, if they were, would require water detecting devices beneath and along the entire lengths of the internal piping which is not practical nor economically feasible. This method also has limited application in outdoor environments although a variant can be found in soil moisture detection for irrigation interrupt applications.
Another method that is used for leak detection in residential and commercial environments is flow detection at the water fixture. In this method, a flow detection device is placed in line with the plumbing pipe line feeding the water fixture. This device incorporates a flow sensor and a normally open shut-off valve as part of the assembly and can be powered either by battery or AC power. This device is designed to detect continuous water flow (e.g., slow drips, open faucet) and/or excessively large flows (e.g., loose fixture fitting) at the fixture. The thresholds for “continuous flow” (e.g., maximum time of flow) or “excessive flow” (e.g., maximum flow rate) are either preset, set by the user, or conceivably could even be a learned behavior setting albeit at a significant increase in unit cost of the device. When either the continuous flow or excessive flow threshold is exceeded at the water fixture, the normally open shut-off valve is activated to close and thereby stopping any further water flow to the water fixture. This method suffers from all of the same shortfalls as the “water detection beneath the water fixture” method previously described (with the exception of sensitivity to placement of the water detection device which is not applicable to this method) making this method equally impractical and equally economically unviable for effectively detecting and stopping water leaks at residential and commercial environments. In addition, if and when there is a leak with a rate flow below the maximum flow rate then water will continue to leak until the maximum time of flow is exceeded, for example 10 minutes. Thus by the time the 10 minutes have elapsed the water damage will have already taken place; for example just a ⅛″ opening in a pipe may spill up to 26 gallons during a 10 minute period (about 2.64 gpm). As an illustrative example, a 140-gallon capacity bathroom spa with a faucet rated at 14 gpm max would take more than 10 minutes to fill at ¾ max flow rate (about 10.5 gpm), yet a ⅛″ leak in the fixture line after the flow detection device would either not be detected (total flow from the device is 13.14 gpm which is less than the 14 gpm max flow) or would be detected after significant water damage has already occurred (after 10 minutes for example); further, and perhaps more importantly, if the ⅛″ leak were right before the flow detection device, the leak would not be detected at all by this method.
Yet another method that is used for leak detection in residential and commercial environments is flow threshold monitoring after the water meter at the water service entrance to a building site. In this method, a flow detection device is placed after the water meter at the water service entrance to a building site but before branching into the internal pipes of the water distribution system. This device incorporates a flow sensor and a normally open shut-off valve as part of the assembly and can be powered either by battery or AC power. This device is designed to detect continuous water flow and/or excessively large flows into the building site. The thresholds for “continuous flow” (e.g., maximum time of flow) or “excessive flow” (e.g., maximum flow rate) are either preset, set by the user, or conceivably could even be a learned behavior setting. When either the continuous flow or excessive flow threshold is exceeded after the meter, the normally open shut-off valve is activated to close and thereby stopping any further water flow to the site. This method has many shortfalls as it more accurately represents detection of continuous or large water consumption at the site rather than leak detection. Since this method measures the totality of the flow into the site's water distribution system it considers a total flow longer than the maximum time of flow setting or a total flow greater than the maximum flow rate setting as a “leak” and will terminate flow. Since water fixtures can operate singly or concurrently, the maximum time of flow setting and the maximum flow rate setting are prone to causing this method to frequently interrupt the flow of water to the site since (a) fixtures operating sequentially but with overlap may have a demand flow for longer than the maximum time of flow, (b) fixtures operating concurrently may have a flow demand greater than the maximum flow rate setting, and (c) a single fixture can operate for longer than the maximum time of flow (e.g., a long shower). In addition, as in the case of the “flow detection at the fixture” method, if and when there is a leak with a rate flow below the maximum flow rate then water will continue to leak until the maximum time of flow is exceeded by which time the water damage will have already taken place.